Devices and sensors for determining ambient light are known. For example, such sensors may be used in many applications such as within devices with a display where the sensor is configured to sense the ambient light levels and thus control the display light levels so that they are not too bright or too dim for the user to view the display and furthermore to optimize power consumption. Typical ambient light sensors require an external power supply. In other words in order to generate a usable output voltage/current value level the sensor is required to be coupled to a power supply, such as a battery or de power line (for example, a USB connection supplying power to the sensor).
These ambient light sensors furthermore consume power even in standby and thus are not acceptable where power consumption is important (or critical) such as in small devices, for example, ‘internet-of-things’ sensor packs and wearables. Furthermore such sensors are not acceptable for devices where providing power or maintaining power supplies are difficult, for example, devices operating in hazardous environments.